1. Field of the Invention
The present invention relates to a method of processing Alaska pollack roe, and more particularly, to a novel method of processing Alaska pollack roe in the production of Alaska pollack roe products such as salted Alaska pollack roe and karashi-mentaiko (Alaska pollack roe pickled in red pepper sauce).
2. Description of the Prior Art
In general, the quality of Alaska pollack roe (roe quality) varies considerably depending on, for example, the season, fishing area and method of fishing, the post-fishing storage conditions and the method of roe collection. For example, the roe of Alaska pollack caught around the spawning season near the spawning ground is overmature and is massed in large ovaries. In contrast, the ovaries of the roe of Alaska pollack in the pre-spawning stage are small, and the roe is immaturely developed.
The quality of the roe also varies depending on the post-fishing storage conditions of the Alaska pollack. For example, when pressure or impact is applied to the body of Alaska pollack, there is a high tendency toward adhesion of bile pigments to and infiltration of hemachromes from the intestinal tract into the ovaries. Also, when the body is overcooled, part or all of the ovaries freeze.
Furthermore, the quality of the roe is affected by the method of roe collection and method of treatment of the roe after collection; for example, the ovaries may be cut, the ovarian membrane torn, the roe granules crushed, or the roe contaminated with internal organs other than the ovaries.
In addition, because the size of the ovaries varies depending on the age and body size of the Alaska pollack, there are greatly differing quality of roe used as the starting material, and it changes easily. In other words, there is wide variation among the starting materials. Accordingly, the methods of preparing Alaska pollack roe products have a disadvantage in that strict selection must be made of the starting material, while the method of processing the material must also be modified depending on the quality of the roe selected. As a result it is difficult to establish definite standard conditions for methods of producing Alaska pollack roe products, and thus under the existing circumstances they are prepared under conditions which are determined based on the perception and experience of the persons in charge for the respective starting materials.
The most important step in the production of Alaska pollack roe products is that of salting, in which additives such as common salt, seasonings and coloring agents, together with water, are added to and mixed with the Alaska pollack roe. The conventional process for this step employs a rotary cask. The rotary cask apparatus rotates the cask at predetermined intervals to thoroughly mix the additives with the Alaska pollack roe placed in the cask, thus promoting the migration (penetration) of the salt, seasonings, coloring agents, etc. into the Alaska pollack roe.
However, the rate of migration of the additives into the roe varies depending on their type and concentration, and therefore uniform migration of the additives to the center of the Alaska pollack roe is not achieved with the above mentioned rotary cask apparatus. In addition, as discussed above, the quality of the resulting Alaska pollack roe products also varies considerably depending on the state of the initial Alaska pollack roe, and this variation in quality has become a problem in the production of Alaska pollack roe products.
Furthermore, since Alaska pollack roe is covered only with a soft ovarian membrane, it is susceptible to physical impact, and particularly shear stress, which causes it to break. Also, because of the ovarian membrane the Alaska pollack ovaries are obtained clinging together in pairs of two (paired ovaries), but upon the slightest impact the ovarian membrane tears to result in unpaired ovaries. Consequently, the greatest care must be taken in handling Alaska pollack roe during the various steps of selection, salting, draining, freezing, etc.
As mentioned above, Alaska pollack roe is associated with the problems of 1. variation in quality and 2. susceptibility to damage of the ovarian membrane, and therefore it is disadvantaged in that the methods for its processing are not always the same, they require a large number of workers and much time, and the automation and simplification of the process is not easy.